Method for controlling compositions of molten pig iron and slag in a blast furnace



1959 KURO KANAMORI ETAL 2,918,365

7 METHOD FOR CONTROLLING COMPOSITIONS OF MOLTEN PIG IRON AND SLAG IN A BLAST FURNACE 2 Sheets-Sheet 1 Filed Aug. 9, 1954 FIG 5 R m: M E

N A K O R U K KATSUJIRO ENDO KORETAKA KODAMA MASAAKI TOKUHISA mmflri .ATTORNEYS Dec. 22, 1959 KU KANAMORI ETAL 9 5 METHOD FOR CO OLL G COMPOSITI s 0F MOLTEN PIG IRON AND SL IN A BLAS URNACE Filed Aug. 9, 1954 2 Sheets-Sheet 2 FIG. 4

INVENTORS KURO KANAMORI KATSUJIRO ENDO KORETAKA DAMA MASAAKI UHISA ATTORNEYS United States Patent METHOD FOR CONTROLLING COMPOSITIONS OF MOLTEN PIG IRON AND SLAG IN A BLAST FURNACE Kuro Kanamori, Suginami-ku, Tokyo-to, Katsujiro Endo, Yawata-shi, Fukuoka-ken, and Koretaka Kodama and Masaaki Tokuhisa, Tobata-shi, Fukuoka-ken, Japan, assignors to Yawata Seitetsu K.K. (stock company), Tokyo-to, Japan, a corporation of Japan Application August 9, 1954, Serial No. 448,496 Claims priority, application Japan August 10, 1953 6 Claims. (Cl. 75-41) This invention relates to a method for controlling composition of molten pig iron and or slag in a blast or shaft furnace.

A principal object of this invention is to provide a method whereby the composition of molten pig iron or slag may be rapidly and simply adjusted without a change of general operating conditions, such as a change in the amount or kind of charge or temperature of air fed into the furnace.

In the case of molten pig iron, said object and other objects of this invention may be accomplished by directly feeding powder of an iron alloy such as ferrosilicon, or ferromanganese, or a desulphurizing agent such as siliconmanganese, calcium silicide or lime and the like into the molten pig iron in the bath of the blast furnace through the blowing tuyere. Feeding of said powder into the molten pig iron can be done so that said powder may be fed together with blown air or nitrogen gas, or the powder may be fed enclosed in a cylinder.

In the case of slag, said object and other objects of this invention may be accomplished by directly introducing, under pressure, any one or mixture of the slag forming agents such as lime, sand and the like into the slag in the bath through a normal tuyere or blowing tuyere by'means of gas under pressure such as compressed air.

The objects and advantage of this invention will be apparent from the following description taken in connection with the drawings, wherein:

Fig. 1 is a vertically sectioned elevation view of a blast furnace for embodying the method A-(a) as de scribed below.

Fig. 2 is a vertically sectioned elevation view of a blast furnace for embodying the method A-(b) as described below.

Fig. 3 and Fig. 4 are vertically sectioned elevation views of a blast furnace for embodying the method of this invention in order to control slag composition.

A. Adjusting of the composition of molten pig iron:

Hitherto, controlling of silicon content and manganese content in the molten pig iron in the bath of a blast furnace has been indirectly carried out by varying the operating conditions such as the amount or kind of charge and the temperature of air fed to the furnace or by varying the furnace condition. This has been because of difiiculty in the operation of directly mixing various substances into the molten pig iron due to high temperature, high pressure and presence of coke layer in the furnace, and also because of low yield due to oxidation at the tuyere. However, with the advance of special blowing methods in the bath of a blast or shaft furnace, wherein oxygen, air or oxygen-enriched air is blown into the bath through a pipe through an inclined tuyere passageway, it has been found that when an amount of silicon or manganese, which is a heat source necessary. for raising thetemperature of the bath in the ease 'o'f'tli'e special blowing method, is insufficient, or

the silicon and manganese content of the bath becomes too low, it is necessary to increase said substances up to a desirable amount rapidly. According to the methods heretofore in use at least 8-10 hours are necessary to increase the contents of said substances up to desirable amounts.

According to this invention, however, iron alloy is, for example, fed directly into the molten pig iron through an inclined blowing tuyere arranged in the furnace wall by means of any one of the following methods, so that increase in necessary substances can be quickly accomplished.

(a) Iron alloy enclosed in an iron cylinder is dropped into the molten pig iron through the inclined blowing tuyere. When said cylinder is prevented from being immersed directly in the molten pig iron due to coke layer produced at said tuyere, said cylinder is forced directly into the molten pig iron by pushing said cylinder by means of a bar.

(b) Mixing of iron alloy into the molten pig iron is carried out by inserting a pipe directly into the bath in the furnace through the inclined blowing tuyere and feeding iron alloy into the molten pig iron through said pipe together with air or nitrogen under pressure.

According to said methods (a) and (b) as described above, iron alloy can enter, in a sure and simple manner, directly into the molten pig iron without any accompanying oxidation at the tuyere position.

Referring to Fig. 1, the blast furnace 5 is provided with an inclined blowing tuyere 1, on the base of which furnace is produced the molten pig iron layer 3 and slag layer 4. Said tuyere is of a size so that a cylinder 2, in which iron alloy is enclosed, may be dropped through said tuyere 1. Said dropping of the cylinder 2 may be facilitated by pushing it through the tuyere 1 by means of a pushing bar 1 capable of passing through said tuyere 1.

In the example shown in Fig. 2, wherein the same parts as those in Fig. 1 are designated by same numerals, a blow pipe 10 is inserted directly into the molten pig iron 3 through the tuyere 1, the upper end of said pipe being connected to the lower opening of a hopper 8 filled with lime powder by a pipe 9 and jointed pipes 11. In said hopper 8 is a jet nozzle 6 positioned so that the opening 7 of said nozzle is opposite the lower opening of said hopper 8.

In the example shown in Fig. 2, when high pressure air or gas is forced through the nozzle 6, the lime powder in the hopper 8 is sucked into the pipe 11 due to the low pressure induced at the opening 7, so that the lime powder can be effectively fed into the molten pig iron together with the air or gas of high pressure through the pipes 11, 9 and 10.

EXAMPLE I The operation was carried out in a small blast furnace having an internal volume of 4.9 m. in accordance with the method (a) as described above. The operation result of said test was as follows:

Operation condition Mixing materials:

Hongkong ore Gumma (Japan) ore Manganese ore 45 kg. (per one charge). 5 kg. (per one charge). 4 kg. (per one charge).

Controlled data Ferrosilicon (before charging):

Si, percent 0.98 Ferrosilicon (after charging of 8 kg.):

After 1.5 hrs. 1.53

After 2.5 hrs. 2.02

After 4 hrs. 2.16

According to said test, it is seen that after charging of ferrosilicon, about 85% of ferrosilicon was mixed into the molten pig iron during about 2 hours and 90% of the same was mixed during about 4 hours, so that it is readily possible to attain the desired condition after as short a period as 2 hours.

Solid lime powder mixed directly into the molten pig iron according to the method of this invention has a desulphurizing action remarkably stronger than that of the lime molten in the molten pig iron, said latter lime having been employed in the methods heretoforein use. Therefore, the method of this invention is effective to prevent sulphur increase, said increase being apt to occur in the case of peroxidation of the molten pig iron due to blowing of air or other gas. Furthermore, the unreacted lime enters into the slag, so that it brings an increase of basicity, whereby controlling of the slag composition becomes passible.

B. Adjusting of slag composition:

The usual controlling of slag composition has been carried out by varying the mixing ratio of the substances to be charged into the furnace. That is, when it is desirable to increase basicity of the slag, the amount of limestone mixed into the charge is increased.

On the other hand, when it is desirable to decrease basicity of the slag, the amount of the substance containing silicic acid which is mixed into the charge is increased. According to the method heretofore in use, at least 8-10 hours are necessary to cause the slag composition to reach a desirable condition. Moreover, when the amount of the limestone mixed in is increased, limehanging is apt to occur at the furnace shaft or bosh resulting in difliculty of operation, so that there is a limit to the increase of the amount of limestone.

When crude starting material of high sulphur content is employed and desulphurization is to be carried out by blowing the bath in the furnace, it is necessary to make the basicity of the slag considerably greater than in the case of normal operation.

According to this invention, however, lime is blown directly into the slag or in the neighbourhood thereof in the bath through a normal tuyere or inclined blowing tufere, so that greater basicity can be readily attained without the lime hanging at the upper part of the furnace.

Furnaces for embodying the method of this invention are shown in Figs. 3 and 4, wherein same parts as those in, Figs. 1 and. 2 are indicated by same numerals.

Referring to Fig. 3, the blast furnace 5 is provided with a normal tuyere 2, on the base of which furnace is produced the moltern pig iron layer 3 and slag layer 4. Said tuyere 2' is connected to the lower opening of a hopper 8 filled with lime powder by a pipe 9 and jointed pipes 11. In said hopper 8 is mounted a jet nozzle 6 with the end opening of said nozzle opposite the lower opening 7 of said hopper 8.

In the example as shown inFig. 3, when high pressure air or gas is forced through the nozzle 6, the lime powder in the hopper 8 is drawn into the pipe 11 due tothe low pressure induced at the. opening 7, so that thelime powder can be effectively fed into the molten pig iron together with the high pressure air or gas through the pipes 11, 9' and the tuyere 2'.

EXAMPLE II The operation was carried out in a small blast furnace having an internal volume of 4.9 m. as shown, in fig. 3. The result of said tcstwas as follows:

Operation condition 45 kg. (per one charge). 5 kg. (per one charge).

Manganese ore 4 kg. (per one charge).

Limestone 33 kg. (per one charge).

Coke 130 kg. (per one charge). Amount of blown air l9 m. /min. Temperature of said air 500 C. Number of times for charging 62. Yield of pig iron 1035 kg.

Controlled data Amount of blown air kg. Blown time 1 hour immediately after tapping.

Before After 2.5 After 6.5 Composition blowing hrs. at hrs. at

slagging out tapping sio, pereent 31. 82 28. so 29. 96 CaO d 41.17 46.00 41.52 Basicity 1.29 1. 63 1. 39

According to said test, it is seen that controlling of slag composition can be quickly accomplished. The apparatus illustrated in Fig. 4 is the same as the apparatus shown in Fig. 3 in the construction and operation except that a blowing pipe 10 is inserted in the inclined blowing tuyere 1.

Since it is obvious that many changes and modifications can be made in the above-mentioned details without departing from the nature and spirit of this invention, it is not limited to said examples and illustrations.

We claim:

1. In smelting pig iron in a blast furnace, the improvement in adjusting the composition of a bath of molten material in said furnace comprising feeding a material in powdered form and mixed with gas directly into a layer of the molten material in the blast furnace, said feeding being in a downward direction from above the level of the surface of said layer and said material in powdered form being added to the molten material to adjust the composition thereof.

2. In smelting pig iron in a blast furnace, the improvement in adjusting the composition of a bath of molten material in said furnace comprising: (1) providing a downwardly inclined tuyere above the level of the molten material and (2) feeding a material in powdered form and mixed with gas through said tuyere directly into the bath of molten material, said material in powdered form being added to the molten material for adjusting the composition thereof.

3. In smelting pig iron in a blast furnace, the improvement in adjusting the composition of a bath of molten material in said furnace comprising: (1) providing a downwardly inclined tuyere above the level of the molten material, (2) inserting a hollow tube through said tuyere into the bath of molten material, ('3) mixing a material in powdered form with compressed air and (4) feeding the resulting mixture through said hollow tube directly into the bath of molten material in said blast furnace, said material in powdered form being added to the molten material for adjusting the composition thereof.

4. In smelting pig iron in a blast furnace, the improvementin adjusting the composition of a bath of molten material in said furnace comprising: (1) providing at least one downwardly inclined tuyere in the wall of the blast furnace above the level of the molten material, (2) inserting a hollow tube through the tuyere and into a layer of the molten material, (3) providing a supply of ma terial inpowdered format the end of the tube outside of h atness, n orc n c mp s ed a h o gh sa d tube drawing with it the powdered material and so feeding said powdered material directly into the bath of molten material in the blast furnace, said powdered material being added to the molten material for adjusting the composition thereof.

5. A method according to claim 4 whereinthe composition of the molten pig iron layer of the bath of molten material in the blast furnace is adjusted, the powdered material is an alloying material, and the tube is inserted directly into the layer of molten pig iron.

6. A method according to claim 4 wherein the composition of the slag layer of the bath of molten material in the blast furnace is adjusted, the powdered material is a slag forming agent, and the tube is inserted directly into the layer of slag.

References Cited in the file of this patent UNITED STATES PATENTS Shunk May 17, 1859 Hubbell Apr. 21, 1874 Pratt Oct. 22, 1889 Brassert July 16, 1912 Wierum June 3, 1913 Wattson Nov. 29, 1938 Hogberg et al Apr. 14, 1942 Howard Sept. 25, 1944 FOREIGN PATENTS Australia Feb. 15, 1938 

2. IN SMELTING PIG IRON IN A BLAST FURNACE, THE IMPROVEMENT IN ADJUSTING THE COMPOSITION OF A BATH OF MOLTEN MATERIAL IN SAID FURNACE COMPRISING: (1) PROVIDING A DOWNWARDLY INCLINED TUYERE ABOVE THE LEVEL OF THE MOLTEN MATERIAL AND (2) FEEDING A MATERIAL IN POWDERED FORM AND MIXED WITH GAS THROUGH SAID TUYERE DIRECTLY INTO THE BATH OF MOLTEN MATERIAL, SAID MATERIAL IN POWDERED FORM BEING ADDED TO THE MOLTEN MATERIAL FOR ADJUSTING THE COMPOSITION THEREOF. 